TANGO was an ONI contingency plan. It was initiated during preparations for Operation: HYPODERMIC, when it was discovered that an AI had breached their defenses and was aware of their plan.

As such, the Circumference has her registration number scrambled, her computer core isolated from the station's computer, and software activated to cease any more AI activity. To the station's computer, the Circumference never existed.[1]

List of appearancesEdit


  1. Halo: Fall of Reach, pages 281-282